Endoscopy is extremely valuable in the evaluation of disorders of the luminal gastrointestinal tract, pancreas, and biliary system. Endoscopy as a medical discipline continues to evolve and is becoming increasingly therapeutic in nature. Minimally invasive endoscopic intervention now is effective in a wide variety of disorders, including gastrointestinal hemorrhage, obstructive diseases of the intestinal or biliary tree, and early detection or prevention of neoplastic disease of the colon and esophagus. The development of EUS technology has expanded greatly the potential utility of endoscopy as a diagnostic and a therapeutic modality, and further technologic advances are anticipated.